WO2009033400A1

WO2009033400A1 - Method and device for indicating data re-transmission when area switching in lte system

Info

Publication number: WO2009033400A1
Application number: PCT/CN2008/072231
Authority: WO
Inventors: Ying Wang; Haijing Hu; Yihua Jiang; Guosheng Zhao; Xunwei Zhao
Original assignee: Da Tang Mobile Communications Equipment Co., Ltd.
Priority date: 2007-09-11
Filing date: 2008-09-02
Publication date: 2009-03-19
Also published as: CN101389119A; US20140301367A1; KR101141124B1; EP2190149A4; EP2190149B1; CN101389119B; JP5034081B2; JP2010539757A; KR20100063788A; US20100177736A1; EP2190149A1; US8797998B2

Abstract

A method and device for indicating data re-transmission when area switching in LTE system, wherein the method comprises the following steps: S_eNB sends PDCP-SDU CN report to T_eNB in order to announce PDCP-SDU SN received, and T_eNB announces PDCP-SDU SN received by S_eNB to UE. Thereby, UE would not re-transmit PDCP-SDU corresponding to received SN, which avoids re-transmission of useless PDCP-SDU, and saves radio resources comparing with prior solutions.

Description

Method and device for instructing data retransmission in cell handover process of LTE system

This application claims priority to Chinese Patent Application No. 200710121647.X, filed on September 11, 2007, entitled "Method and Apparatus for Data Retransmission in LTE System Cell Switching Process", all of which The content is incorporated herein by reference.

Technical field

The present invention relates to the field of LTE (Long Time Evolution) system technology for mobile communications, and in particular, to a method and apparatus for instructing data retransmission in a cell handover process of an LTE system. Background technique

In the cell handover of the LTE system, the UE (User Equipment) assisted network control idea, that is, the "measurement-report-decision-execute" step is still used. When the S-eNB (Source Evolved Node B) determines the handover of the UE to the target cell according to the measurement report of the UE and the Target Evolved Node B (Target Evolved Node B), it directly passes through the X2 interface and the T-eNB. Performing information exchange to complete resource preparation of the target cell; then commanding the UE to switch to the target cell; after the handover is successful, the T-eNB notifies the S-eNB to release the radio resource of the original cell. In addition, the S-eNB also transmits the data that has not been transmitted to the T-eNB, and updates the node relationship between the user plane and the control plane.

Referring to FIG. 1 , it is a flow chart of cell handover in an existing LTE system, which mainly includes:

[1] S_eNB configures the measurement process of the UE;

[2] The UE sends a measurement report to the S_eNB;

[3] The S_eNB makes a UE handover decision according to the measurement report and the RRM (Radio Resource Management) information;

[4] The S_eNB sends a handover request to the T_eNB;

[5] After receiving the S_eNB handover request, the TeNB performs an admission control (Admission Control) process based on the QoS (Quality of Service) information received from the System Architecture Evolution (SAE);

[6] The T eNB sends a handover request acknowledgement message to the S_eNB;

[7] The S_eNB sends a handover command message to the UE, instructing the UE to perform handover;

[8] The UE sends a synchronization message to the T_eNB; [9] The T-eNB feeds back a synchronization reply message to the UE, where the synchronization reply message includes an UL resource allocation message and a time advance (time advance);

[10] After the UE successfully accesses the target cell, the UE sends a handover complete confirmation message to the T-eNB.

On the user plane, in order to avoid the loss of the uplink data of the UE during handover, the uplink data is transmitted in order, and the uplink data forwarding scheme is adopted, that is, the steps in FIG. 1 above.

Performed between [7] and step [8] (marked by dotted lines in the figure). In summary, data forwarding refers to: S eNB forwards the received out-of-order PDCP-SDU (Packet Data Convergence Protocol - Service Data Unit) to the T-eNB, and adds SN (Sequence Number), and then the T-eNB sends the received PDCP-SDU to the S-GW. The transmission of the upper layer PDU (Packet Unit) in sequence is based on the continuous PDCP-SN and is guaranteed by the PDCP layer to provide reordering. In the uplink, the reordering function of the PDCP layer of the T-eNB ensures the in-order delivery of the uplink PDCP-SDU.

In the current LTE system, the ARQ/HARQ (Automatic Repeat Request/Hybrid Automatic Repeat Request) mechanism is adopted for the radio interface, and the ordered PDCP-SDU successfully received by the S-eNB is used. , will feedback ACK to the UE. On the UE side, the PDCP-SDU that has not received the ACK is retransmitted to the T-eNB. It is not difficult to analyze that the UE does not receive the ACK of the PDCP. The first one is that the S-eNB does not receive the PDCP due to the network or the like, and the ACK is not fed back to the UE. The second is that the S-eNB successfully receives the ACK. Ordered PDCP, but the feedback ACK was not successfully sent to the UE due to network reasons. In the second case described above, the UE will be inefficiently transmitted to the T-eNB, and valuable radio resources are wasted. The following two cases are analyzed by examples.

Referring to FIG. 2, it is a scenario in which the UE repeatedly transmits PDCP-SDU to cause invalid waste. The S_eNB successfully receives the data 1, 2, 3 from the UE, and transmits the data to the S-GW through the S1 interface. It is assumed that the UE only receives the ACK of the data 1 fed back by the network side, and does not receive the ACK corresponding to the data 2 and 3. The UE will continue to send data 2, 3 to the T-eNB, and the T eNB will also send the data 2 and 3 retransmitted by the UE to the S-GW, thereby causing the EPC (Evolved Packet Core) system. Receive duplicate data and waste valuable air interface radio resources.

Referring to FIG. 3, another scenario in which the UE repeatedly transmits PDCP-SDU causes invalid waste, where the UE sends data a, b, c, and d to the S-eNB, but the data b is in error in transmission, S— eNB Only the data a, c and d are received, and the data c and the data d are out of order, then according to the existing data forwarding scheme, the S-eNB sends the ordered data a to the S-GW (Service Gateway, Service Gateway). The buffered data c and the data d are buffered in the Buffer, and then the data c and the data d are sent to the T-eNB, and the T-eNB provides the S-GW. Also assume that the UE does not receive an ACK for data c and d. At this time, the UE will only receive the ACK of the data a. Since the ACK of the data b, c and d is not received, the UE will retransmit the data b, c and d to the T-eNB, obviously, for the data c and the data d Repeated transmission will occur: On the one hand, the S-eNB will send the buffered data c and data d to the T-eNB. On the other hand, the UE will also retransmit the data c and data d to the T-eNB due to the absence of the ACK. , resulting in waste of resources.

Summary of the invention

In view of the above, the present invention provides a method for indicating data retransmission in a cell handover process of an LTE system, so as to solve the problem that the UE repeatedly transmits unnecessary PDCP-SDUs in the existing solution and wastes radio resources;

Corresponding to the above method, the present invention further provides means for instructing control data retransmission in the cell handover process of the LTE system, namely, an eNB, and a UE.

To this end, the present invention uses the following technical solutions:

A method for instructing data retransmission in a cell handover process of an LTE system, comprising: S-eNB transmitting a PDCP-SDU SN report to a T eNB, notifying a received PDCP-SDU SN; T-eNB notifying the UE of the S-eNB Received PDCP-SDU SN.

The method further includes: the UE rejects the retransmission queue according to the received PDCP-SDU SN.

The PDCPSDU that the S_eNB has received retransmits only the remaining PDCPSDUs in the queue to the T-eNB.

The T-eNB informs the UE that the S-eNB has been configured by using a synchronization reply message, RRC (Radio Resource Control) information, an RLC message, or a MAC (Media Access Control) message. Received PDCP-SDU SN.

Preferably, when the UE synchronizes to the T-eNB, the T-eNB determines whether the PDCP-SDU has been received.

The SN reports, if yes, sends a synchronization reply message carrying the PDCP-SDU SN that the S-eNB has received to the UE; otherwise, sends a synchronization reply message that does not include the PDCP-SDU SN to the UE.

Or, when the UE synchronizes to the T-eNB, the T-eNB determines whether the PDCP-SDU SN report has been received, and if so, sends a synchronization reply message carrying the PDCP-SDU SN that the S-eNB has received to the UE; Otherwise, wait, if the PDCP-SDU SN report is not received within the preset time period, send a synchronization reply message that does not include the PDCP-SDU SN to the UE, if the PDCP-SDU is received within the preset time period The SN reports, and sends a synchronization reply message carrying the PDCP-SDU SN that the S-eNB has received to the UE.

Or, when the UE synchronizes to the T-eNB, the T-eNB determines whether the PDCP-SDU SN report has been received, and if so, sends a synchronization reply message carrying the PDCP-SDU SN that the S-eNB has received to the UE; otherwise, to the UE Send a synchronous reply message that does not contain the PDCP-SDU SN, and receive it

After the PDCP-SDU SN reports, it immediately triggers an RRC message, an RLC message, or a MAC message to the UE, and notifies the UE that the S-eNB has received the PDCP-SDU SN.

The timing at which the S-eNB sends the PDCP-SDU SN report to the T-eNB is when the handover command acknowledgement message fed back by the UE is received, or the handover command acknowledgement message is not received, but the handover is sent to the UE. When the time of the command message has reached the predetermined value.

An eNB for instructing control data retransmission in a cell handover process of an LTE system, including an X2 interface unit, and a UE interface unit that communicates with the UE, further includes: a report assembly unit and a message assembly unit, where the report assembly unit is configured to follow Decoding a PDCP-SDU received by the UE interface, assembling a PDCP-SDU SN report including the SN of the received PDCP-SDU, the PDCP-SDU SN report being sent to the T-eNB through the X2 interface unit;

The message assembling unit is configured to assemble, according to the PDCP-SDU SN report received by the X2 interface unit, a message including a PDCP-SDU SN that has been received by the S-eNB, and send the message to the UE interface unit. UE.

The information assembled by the message assembling unit is a synchronous reply message, an RRC message, an RLC message, or a MAC message.

A UE that controls data retransmission in a cell handover process of an LTE system, includes an eNB interface unit that communicates with an S-eNB or a T eNB, and a retransmission queue that buffers a PDCP-SDU, and further includes a message parsing unit and a queue collating unit; The eNB interface unit is configured to receive a message from the T-eNB, where the message indicates a PDCP-SDU SN that the S-eNB has received; the message parsing unit parses the message, and learns that the S-eNB has received a PDCP-SDU SN; the queue sorting unit culls the PDCP-SDU SN that the S-eNB has received from the retransmission queue, and the eNB interface unit only retransmits the remaining PDCP-SDUs in the queue to the T-eNB . The message indicating that the S-eNB has received the PDCP-SDU SN refers to a synchronous reply message, an RRC message, an RLC message, or a MAC message.

The technical effects of the above technical solutions are analyzed as follows:

In the original LTE system cell handover scheme, the UE retransmits the PDCP to the T-eNB as long as the ACK of the PDCP is not received. However, in the present invention, the UE further determines whether the T-eNB is received. Indicates that the S-eNB has received the PDCP-SN of the PDCP. If the ACK of a PDCP is not received, but the PDCP-SN indicating that the PDCP has been received is received, the UE does not retransmit the PDCP, thereby avoiding unnecessary transmission of unnecessary PDCP, compared to the existing one. The solution can effectively save wireless resources.

DRAWINGS

1 is a schematic diagram of cell switching in a LTE system in the prior art;

2 is a first schematic diagram of a UE repeatedly transmitting data in the prior art;

3 is a second schematic diagram of a UE repeatedly transmitting data in the prior art;

4 is a schematic view of a first embodiment of a method according to the present invention;

Figure 5 is a flowchart of Embodiment 1 of the method of the present invention;

6 is a schematic diagram of an example of an embodiment of a method according to the present invention;

7 is a flow chart of Embodiment 2 of the method of the present invention;

Figure 8 is a flowchart of Embodiment 3 of the method of the present invention;

9 is a schematic structural diagram of an S-eNB device according to the present invention;

10 is a schematic structural diagram of a T-eNB device according to the present invention;

FIG. 11 is a schematic structural diagram of a UE device according to the present invention.

detailed description

The core of the present invention is that, in the process of UE cell handover, a procedure is added, that is, the S-eNB informs the UE through the T-eNB that which PDCP-SDUs have been successfully received by the S-eNB, and the UE does not receive the ACK of these PDCP-SDUs even if the UE does not receive the PDCP-SDUs. , there is no need to retransmit.

Still further, the invention is implemented in the following manner:

1] The S_eNB sends a PDCP-SDU SN report to the T-eNB to inform the T-eNB of the PDCP-SDU SN that it has received (including all SNs of the ordered and unordered PDCPSDUs);

2] According to this report, the T_eNB resends the PDCP-SDU SN to the UE, and informs the UE which The PDCP-SDU has been received;

3] The UE does not retransmit the PDCP-SDU according to the received PDCP-SDU SN.

In the original LTE system cell handover scheme, the UE retransmits the PDCP-SDU to the T-eNB as long as the ACK of the PDCP-SDU is not received. However, in the present invention, the UE further determines whether the T is received. The SN sent by the eNB indicates that the S-eNB has received the SN of the PDCP-SDU. If the ACK of a PDCP-SDU is not received, but the PDCP-SDU SN indicating that the PDCP-SDU has been received is received, the UE does not retransmit the PDCP-SDU, thereby avoiding unnecessary transmission of unnecessary PDCP-SDU, compared to existing solutions, can effectively save wireless resources.

The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

It is not difficult to analyze from the above, the present invention adds a signaling in the cell handover process to transmit

S - The PDCP-SDU SN received by the eNB. For these PDCP-SDUs, the UE will not retransmit. In order to make the whole process clearer, the following describes the LTE system cell handover procedure, that is, an improved scheme based on the cell handover introduced in the background art.

Referring to FIG. 4, which is a schematic diagram of a cell handover in an LTE system according to Embodiment 1, the cell handover includes: Step 401: S-eNB configures a measurement process of the UE according to the roaming restriction information;

The measurement information provided by the S_eNB can assist in controlling the UE's function of connecting mobility.

Step 402: The UE sends a measurement report to the S-eNB.

Step 403: The S-eNB performs a cell handover (Handover) of the UE according to the measurement report reported by the UE and the RRM information to make a handover decision.

Step 404: The S-eNB sends a handover request message carrying the necessary information to the T-eNB.

(Handover Request), so that the T-eNB is ready to switch resources, and the handover request message further indicates whether the system supports DL/UL data forwarding, and the handover request message further includes a SAE bearer context;

The SAE bearer context includes TNL (Transport Network Layer) information of the S-GW for transmitting uplink data, QoS information carried by the SAE, and the like.

Step 405: The T-eNB performs an admission control (Admission Control) process based on the received SAE bearer QoS information.

Step 406: The T-eNB sends a Handover Request Acknowledge message to the S-eNB while preparing to switch resources. The handover request acknowledgement message includes a transport network layer address and a TEID (Tunnel End Point Identifier) that are allocated by the T-eNB to support DL/UL data forwarding.

Step 407: After receiving the handover request acknowledgement message of the T-eNB, the S-eNB sends a handover command message (Handover Command) to the UE, and instructs the UE to perform handover.

The handover command message includes a new RNTI (Radio Network Temporary Identity), a handover starting time, and a SIB (System Information Block) of the T_eNB.

After receiving the handover command message of the S-eNB, the UE will stop transmitting the PDCP-SDIL to the S-eNB. The UE may use the RLC (Radio Link Control) confirmation process or ensure the handover command message through other mechanisms. Correct reception.

After the S_eNB sends the handover command message, it starts to perform UL/DL data forwarding, that is, the PDCP-SDU sent by the UE is buffered into the Buffer and sent to the T-eNB.

Step 408: After receiving the acknowledgment message of the RLC layer of the handover command message, or waiting for a period of time without the RLC acknowledgment message, the eNB sends a PDCP-SN report to the T-eNB through the interface X2, and notifies the T- The SN of all PDCP-SDUs that the eNB has received;

The period of time mentioned above for not receiving the RLC acknowledgment message is determined by the possible starting time in the handover command message.

Step 409: After the start time of the handover command message arrives, the UE sends a synchronization message to the T-eNB, requesting synchronization with the T-eNB. Thereafter, the T-eNB starts to acquire the time advance of the UE.

Step 410: After the UE synchronizes to the T-eNB, the T-eNB sends a synchronization reply message including a UL resource allocation message, a time advance, and a PDCP-SN in the PDCP-SN report to the UE; due to the delay of the X2 interface, After the UE synchronizes to the T-eNB, the T-eNB may not receive the PDCP-SN report sent by the S_eNB in time. If the T-eNB does not receive the PDCP-SN report when replying to the UE, the T-eNB does not include the PDCP-SN report. PDCP-SN, otherwise it contains PDCP-SN.

The UE will remove the corresponding PDCP from the retransmission queue according to the indication of the PDCP-SN, and achieve the purpose of saving the scarce resources of the air interface; if there is no PDCP-SN indication, the UE also processes according to the original manner, and the solution provided by the present invention is The prior art is easily compatible.

Step 411: After successfully accessing the target cell, the UE sends a handover acknowledgement message (Handover Confirm) to the T-eNB to inform the completion of the handover process. Thus, the present invention focuses on adding step 408, as well as improvements to step 410, and also includes the UE's subsequent retransmission of PDCP.

Referring to FIG. 5, a flowchart of Embodiment 1 includes:

Step 501: After transmitting the handover command message to the UE, the S-eNB sends a PDCP-SN report to the T-eNB when the RLC acknowledgement message is to be received, or when waiting for a period of time;

Step 502: When the UE synchronizes to the T-eNB, does the T-eNB receive the PDCP-SN report sent by the S-eNB? If yes, go to step 503 to branch, otherwise, go to step 505 to branch; Step 503: The T eNB sends a synchronization reply message carrying the PDCP-SN to the UE; Step 504: The UE never receives the ACK from the PDCP retransmission queue. The PDCP SDU corresponding to the PDCP-SDU SN is removed, and only the remaining PDCP-SDUs in the retransmission queue are retransmitted to the T-eNB;

Step 505: The T-eNB sends a synchronization reply message to the UE, where the synchronization reply message is consistent with the existing solution, including a UL resource allocation message and a time advance;

Step 506: The UE retransmits all PDCP-SDUs that have not received the ACK to the T-eNB. The present invention can be used to prevent the UE from repeatedly transmitting the useless PDCP-SDIL to the T-eNB. The scenario shown in FIG. 3 is taken as an example to illustrate that the UE sends data &, b, c, and d to the S-eNB, but the data b In the transmission error, the natural UE will not receive the ACK of the data b, the S-eNB only receives the data &, c and d, and the data c and the data d are out of order, and it is assumed that the UE does not receive the ACK of the data c and d . Then, according to the solution of the embodiment, the S-eNB adds the step of assembling the PDCP-SDU SN report of the received PDCP-SDU in the existing process processing, and the PDCP-SDU SN report includes the data, the SN of the c and the d. At the appropriate time (when receiving the RLC acknowledgment message, or waiting for a period of time), the S-eNB will provide this report to the T-eNB, and the T-eNB informs the UE which PDCP-SDU has been The S-eNB successfully receives, ie, data a, c, and d, and does not have to retransmit for these data. On the UE side, only the ACK of the data a will be received, and for the data 1), c and d will be placed in the retransmission queue for retransmission, but for the data c and the data d, since the synchronization reply message is known as S- The eNB has successfully received, so the UE will reject the data c and d from the retransmission queue, that is, only retransmit the erroneous data b to the T-eNB. Compared with the existing scheme, it is avoided to repeatedly transmit data c and d (S-eNB will forward data to T-eNB through data transmission), which saves valuable air interface radio resources. For the scenario of Figure 3, the processing of this embodiment is shown in Figure 6.

The following describes the second embodiment of the method of the present invention: In the first embodiment, if the PDCP-SDU SN is not received, after the UE synchronizes, the T-eNB sends a reply message to the UE after receiving the PDCP-SDU SN within the preset time period, and provides the PDCP to the UE as much as possible. -SDU SN, ensuring that the UE does not retransmit redundant PDCP-SDIL

Referring to FIG. 7, the flow chart of the second embodiment includes:

Step 701: After transmitting the handover command message to the UE, the S-eNB sends a PDCP-SDU SN report to the T-eNB when the RLC acknowledgement message is to be received, or when waiting for a period of time;

Step 702: When the UE synchronizes to the T-eNB, does the T-eNB receive the PDCP-SDU SN report sent by the S-eNB? If yes, go to step 703 to branch, otherwise, perform step 705;

Step 703: The T eNB sends a synchronization reply message carrying the PDCP-SDU SN to the UE. Step 704: The UE removes the PDCP-SDU corresponding to the PDCP-SDU SN from the PDCP retransmission queue that has not received the ACK, and only retransmits the queue. The remaining PDCP-SDUs are retransmitted to the T-eNB;

Step 705: In the preset time period, whether the PDCP-SN report is received, if yes, step 703 is performed, if the waiting time has exceeded the time period value, step 706 is performed;

There are several reasons for not receiving the PDCP-SN report, such as the X2 interface delay, or the network transmission congestion, or the PDCP-SDU SN that has been received but cannot be correctly parsed. In this case, step 706 is also performed;

Step 706: The T-eNB sends a synchronization reply message to the UE, where the synchronization reply message is consistent with the existing solution, and includes only the UL resource allocation message and the time advance;

Step 707: The UE retransmits all PDCP-SDUs that have not received the ACK to the T-eNB. Embodiment 2 On the basis of the first embodiment, when the PDCP-SDU SN report is not obtained, the T-eNB does not immediately send the synchronization reply message, but waits for a period of time, further ensuring that the UE can receive the PDCP-SDU SN. Synchronize reply messages to ensure more efficient wireless resource savings.

The following describes the third embodiment of the present invention:

The difference from the above two embodiments is also the processing of the T eNB after step 408. In this embodiment, if the T-eNB has received the PDCP-SDU SN report of the S-eNB before the UE synchronizes, the reply to the UE is The message carries the PDCP-SDU SN; if the T-eNB does not receive the PDCP-SDU SN report of the S-eNB after the UE synchronization, it does not carry the reply message sent to the UE. The PDCP-SDU SN, but after receiving the PDCP-SDU SN report, immediately triggers an RRC message, an RLC message, or a MAC message carrying the PDCP-SDU SN to the UE. Accordingly, the UE removes the RRC and RLC from the retransmission queue. The PDCP-SDU corresponding to the PDCP-SDU SN carried in the message or the MAC message retransmits only the remaining PDCP-SDUs in the queue to the T-eNB.

Referring to FIG. 8, the flowchart of the third embodiment includes:

Step 801: After sending the handover command message to the UE, the S_eNB sends a PDCP-SDU SN report to the T-eNB when the RLC acknowledgement message is to be received, or when waiting for a period of time;

Step 802: When the UE synchronizes to the T-eNB, does the T-eNB receive the PDCP-SDU SN report sent by the S-eNB? If it has been received, go to step 803 to branch, otherwise, perform step 805;

Step 803: The T eNB sends a synchronization reply message carrying the PDCP-SDU SN to the UE. Step 804: The UE rejects the PDCP-SDU from the PDCP-SDU retransmission queue that has not received the ACK.

The PDCP-SDU corresponding to the SN retransmits only the remaining PDCP-SDUs in the retransmission queue to the T-eNB; Step 805: The T-eNB sends a synchronization reply message to the UE, and the synchronization reply message is consistent with the existing scheme, including only the UL. Resource allocation message and time advance;

Step 806: The T eNB receives the PDCP-SDU SN report sent by the S-eNB. Step 807: Immediately send an RRC message, an RLC message, or a MAC message carrying the PDCP-SDU SN to the UE.

Step 808: The UE removes the PDCP-SDU corresponding to the PDCP-SDU SN carried in the RRC, the RLC message, or the MAC message from the retransmission queue, and retransmits only the remaining PDCP-SDUs in the queue to the T-eNB.

In this embodiment, when the PDCP-SN report is not received, the T-eNB still sends the synchronization reply message in the prior art to the UE, which is well compatible with the prior art, and is triggered when the PDCP-SN report is obtained. The RRC, RLC message or MAC message informs the UE to minimize the possibility of retransmitting redundant PDCP-SDU and ensure the effective and rational use of the radio resources.

Referring to FIG. 9, the structure of the S-eNB in the present invention includes a report assembling unit 903 in addition to the X2 interface unit 901 communicating with the T-eNB and the UE interface unit 902 communicating with the UE.

The report assembling unit 903 is mainly responsible for receiving according to the UE interface unit 802. PDCP-SDU, assembling a PDCP-SDU SN report containing the SN of the received PDCP-SDU, the PDCP-SDU SN reporting through the X2 interface unit 901 at the appropriate time (when receiving the RLC acknowledgement message, or waiting It is sent to the T-eNB for a period of time.

Referring to FIG. 10, a schematic diagram of a T-eNB structure in the present invention includes a message assembling unit 1003 in addition to an X2 interface unit 1001 that communicates with the S-eNB and a UE interface unit 1002 that communicates with the UE.

The message assembling unit 1003 is mainly responsible for assembling and including the S-eNB has received

PDCP-SDU SN message. Based on the function of each unit in the existing T-eNB, the X2 interface unit 1001 is further configured to receive a PDCP-SDU SN report sent by the S-eNB, where the report includes a PDCP-SDU SN that the S-eNB has received. The UE interface unit 1002 is further configured to send a message assembled by the information assembling unit 1003 to the UE. The information assembled by the message assembly unit 1003 refers to a synchronous reply message,

RRC message, RLC message or MAC message.

FIG. 11 is a schematic diagram of a UE structure in the present invention. In addition to the eNB interface unit 1101 that communicates with the S-eNB or the T-eNB, and the retransmission queue 1102 in which the PDCP-SDU is buffered, the message parsing unit 1103 and the queue are also included. Organizing unit 1104.

The eNB interface unit 1101 is further configured to receive an indication from the T-eNB based on the existing function.

The message of the PDCP-SDU SN that the S_eNB has received. The message parsing unit 1103 is mainly responsible for parsing the message and knowing the SN of the PDCP-SDU that the S-eNB has received. Queue unit

1104 is mainly responsible for removing the PDCP-SDU SN that the S-eNB has received from the retransmission queue 1102. Naturally, the eNB interface unit 1101 only retransmits the remaining PDCP-SDUs in the retransmission queue 1102 to the T-eNB. The message indicating that the S-eNB has received the PDCP-SDU SN refers to a synchronous reply message, an RRC message, an RLC message or a MAC message.

For details of the implementation of the S-eNB, the T-eNB, and the UE provided by the present invention, refer to the foregoing method embodiments, and details are not described herein again.

The above is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It should be considered as the scope of protection of the present invention.

Claims

Rights request

A method for instructing data retransmission in a cell handover process of an LTE system, which is characterized by:

The source evolved base station S-eNB sends a packet data convergence protocol-service data unit sequence number PDCP-SDU SN report to the target evolved base station T-eNB, and informs the received PDCP-SDU SN;

The T eNB informs the user equipment UE that the S-eNB has received the PDCP-SDU SN.

2. The method according to claim 1, further comprising:

The UE removes the PDCP-SDU that the S-eNB has received from the retransmission queue according to the received PDCP-SDU SN, and retransmits only the remaining PDCP-SDUs in the queue to the T-eNB.

The method according to claim 1 or 2, wherein the T-eNB informs the UE by using a synchronization reply message, a radio resource control RRC message, a radio link control RLC message or a medium access control MAC message. The S-eNB has received the PDCP-SDU SN.

4. The method of claim 3, wherein

When the UE synchronizes to the T-eNB, the T-eNB determines whether the PDCP-SDU SN report has been received, and if so, sends a synchronization reply message carrying the PDCP-SDU SN that the S-eNB has received to the UE; otherwise, not transmitting to the UE Contains a synchronous reply message for the PDCP-SDU SN.

5. The method of claim 3, wherein

When the UE synchronizes to the T-eNB, the T-eNB determines whether the PDCP-SDU SN report has been received, and if so, sends a synchronization reply message carrying the PDCP-SDU SN that the S-eNB has received to the UE; otherwise, if, if If the PDCP-SDU SN report is not received within the preset time period, the UE sends a synchronization reply message that does not include the PDCP-SDU SN, and if the PDCP-SDU SN report is received within the preset time period, the UE is sent to the UE. The transmission carries a synchronization reply message that the S-eNB has received the PDCP-SDU SN.

6. The method of claim 3, wherein

When the UE synchronizes to the T-eNB, the T-eNB determines whether the PDCP-SDU SN report has been received, and if so, sends a synchronization reply message carrying the PDCP-SDU SN that the S-eNB has received to the UE; otherwise, not transmitting to the UE The synchronization reply message of the PDCP-SDU SN is included, and after receiving the PDCP-SDU SN report, the RRC message, the RLC message or the MAC message is immediately triggered to the UE, and the UE receives the PDCP-SDU SN to inform the UE.

7. A method according to claim 1 or 2, characterized in that

The timing at which the S-eNB sends the PDCP-SDU SN report to the T-eNB is when the handover command acknowledgement message fed back by the UE is received, or the handover command acknowledgement message is not received, but the handover command message is sent to the UE. When the time has reached the predetermined value.

8. An eNB for instructing control data retransmission in a cell handover process of an LTE system, comprising an X2 interface unit, and a UE interface unit that communicates with the UE, and further comprising: a report assembly unit and a message assembly unit:

The report assembling unit is configured to assemble a PDCP-SDU SN report including the SN of the received PDCP-SDU according to the PDCP-SDU received by the UE interface, where the PDCP-SDU SN report is sent by using the X2 interface unit To the T eNB;

The eNB according to claim 8, wherein the information assembled by the message assembling unit is a synchronization reply message, an RRC message, an RLC message or a MAC message.

10. A UE for controlling data retransmission in a cell handover process of an LTE system, comprising an eNB interface unit that communicates with an S-eNB or a T eNB, and a retransmission queue that buffers a PDCP-SDU, wherein the message parsing is further included. Unit and queue unit;

The eNB interface unit is configured to receive a message from the T-eNB, where the message indicates that the S-eNB has received the PDCP-SDU SN;

The message parsing unit parses the message to learn the PDCP-SDU SN that the S-eNB has received;

The queue organizing unit removes the PDCP-SDU SN that the S-eNB has received from the retransmission queue, and the eNB interface unit only retransmits the remaining PDCP-SDUs in the queue to the T-eNB.

The UE according to claim 10, wherein the indication that the S-eNB has received

The message of the PDCP-SDU SN refers to a synchronous reply message, an RRC message, an RLC message, or a MAC message.